Physicists working in a lab under a mountain in Italy have been getting some truly extraordinary results. For the past three years, they have been recording the arrival times of neutrinos sent by the Cern particle physics laboratory 730km away, and their data suggest the subatomic particles are travelling through the Earth faster than the speed of light.

If this finding can be verified, it would mean Einstein’s famous declaration that nothing can travel faster than the speed of light in a vacuum is wrong. The laws of physics as we know them state that information cannot be communicated faster than the speed of light. What’s going on?

According to Subir Sarkar, head of particle theory at Oxford University: “If this is proved to be true it would be a massive, massive event. It is something nobody was expecting. “The constancy of the speed of light essentially underpins our understanding of space and time and causality, which is the fact that cause comes before effect.”

Can the results be trusted? What other likely explanations are there for the findings? Are journalists jumping the gun when they report that the speed of light rule has been broken?
Supposing the results can be repeated by other labs, would physicists need to tear up the rule book and start again?

If the result is proved correct – and that is still a big if – you have to go into some relatively uncharted areas of theoretical physics to start explaining it. One idea is that the neutrinos are able to access some new, hidden dimension of space, which means they can take shortcuts. Joe Lykken of Fermilab told the New York Times: “Special relativity only holds in flat space, so if there is a warped fifth dimension, it is possible that on other slices of it, the speed of light is different.”

Alan Kostelecky, an expert in the possibility of faster-than-light processes at Indiana University, put forward an idea in 1985 predicting that neutrinos could travel faster than the speed of light by interacting with an unknown field that lurks in the vacuum. “With this kind of background, it is not necessarily the case that the limiting speed in nature is the speed of light,” he told the Guardian. “It might actually be the speed of neutrinos and light goes more slowly.”

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